In conventionally employed techniques for producing ethanol or the like, after saccharification of biomass such as wood or the like by dilute sulfuric acid and concentrated sulfuric acid, solid-liquid separation is performed, and the liquid phase is neutralized and used as a raw material of ethanol fermentation or the like (Patent Document 1, Patent Document 2).
Furthermore, production of raw materials for the chemical industry (for example, lactic fermentation and the like) using saccharides as a starting material is also considered.
Here, biomass refers to accumulation of organisms or organic matter derived from organisms that are incorporated in the substance circulation system of the global biosphere (see JIS K 3600 1258).
Here, sugarcane, corn, and the like currently used as raw materials of alcohols are those originally used for foods, but using these food resources as long-term, stable industrial resources is not desirable from the perspective of an effective foodstuff lifecycle.
For this reason, an important problem is the effective utilization of cellulose resources like herbaceous biomass and wood biomass, which are thought to be useful resources for the future.
In cellulose resources, cellulose content varies from 38 to 50%, hemicellulose component varies from 23 to 32%, and lignin components, which do not serve as fermentation raw materials, also varies from 15 to 22%. Since a study for industrialization has posed numerous problems, in a current state, raw materials are presumed to be fixed and a technology of production system that takes into consideration the versatility of raw materials is not disclosed.
Additionally, in the methods that are more disadvantageous for fermentation raw materials than for starch raw materials to begin with, there is little significance in a production system that considers raw materials to be fixed, considering objectives such as waste problems and global warming prevention measures. The methods need to be widely applicable to general waste. In the current state, the efficiency of enzymatic saccharification itself is poor, which is considered to be a problem for the future. The saccharification rate by acid treatment is also low, around 75% (based on saccharifiable components), due to excessive decomposition of saccharides due to overreaction and the like. Therefore, the ethanol production yield from cellulose-based resources is about 25% (Patent Document 3).
Furthermore, in the conventional art of Patent Documents 1 to 3, a phenomenon has been occurred in which secondary reaction products causes inhibition of enzymatic saccharification and saccharide yield declines. Therefore, hydrothermal decomposition apparatuses that remove enzymatic saccharification-inhibitor substances and increase enzymatic saccharification capability by the cellulose main constituent have been proposed (Patent Documents 4 to 6).